One downside of many wearable fitness devices is that they are too bulky to be comfortable, especially while exercising. Smart watches, rings and other wearable smart jewelry solve that issue, but some people either find them unattractive or don’t want to replace watches and other jewelry they already own.

The AmpStrip from FitLinxx in Westborough, MA eliminates both of those issues. The thin, waterproof device is only 3.5 inches long, 1 inch wide, less than one quarter of an inch thick including its adhesive, and weighs less than 4 ounces. Despite being as discrete and comfortable as a Band-Aid when stuck to the user’s torso, it’s able to track heart rate and activity around the clock with accuracy, the company claims.

The device is compatible with Bluetooth LE mobile devices including smartphones and tablets, and the company’s goal is to make it work in conjunction with smart watches, too, including those from Apple and Samsung. Backers who provide $119 in financing to AmpStrip’s Indiegogo campaign will get an AmpStrip when it ships in June, along with a wireless charging station and 30 adhesives, good for 3-6 months depending on how often the user opts to replace them. FitLinxx is looking to raise $50,000 to make further innovations to the device, which marks its first foray into consumer products.

It is a crowded market, but AmpStrip’s design and comfort level should give it a leg up on rivals. Even the LEO flexible leg band appears to be more bulky than AmpStrip. But the FitLinxx product does come saddled with necessary refills. On top of the initial cost, users will have to fork up $30 each time they need another 3-6 month supply of adhesives.